In practice, extracorporeal blood circuits undergo preparation prior to being used in a medical treatment method. The treatment apparatus utilized for the treatment with the extracorporeal circuit is in practice adapted to the upcoming treatment modality and/or to the utilized (disposable) articles such as blood circuit or blood filter before the beginning of the treatment. For this purpose, the extracorporeal blood circuit is usually filled with a fluid (for example, a substituate solution) before its use and flushed herewith in order to remove possibly present production residues and/or air bubbles from the extracorporeal blood circuit; Occasionally, the treatment apparatus is set at a defined treatment modality at which it should or may be used for the treatment, or which type or which size the utilized blood filter or blood circuit is. It is necessary to know at least one parameter both for determining a minimum flush volume for the blood circuit and for adapting the treatment apparatus to the utilized (disposable) articles.